Pump-unloading device.



P. L. CRITTENDEN & L. D. SAUNDERS.

PUMP UNLOADING DEVICE.

APPLICATION FILED JULY 12. 1915.

1,224, 14:6. Patented May 1, 1917.

2 SHEETS-SHEET I WITNESSES O INVENTQH S ms name's PETERS co.. PN010-LITNO.WASHINC you, n c.

P. L. CRITTENDEN & L. D. SAUNDERS.

PUMP UNLOADING DEVICE.

APPLICATION FlLED JULY 12. 19:5.

1,224, 146. Patented May 1, 1917.

2 SHEETS-SHEET 2- PHILIP L. CRITTENDEN, OF EDGEWOOI), AND LAWRENCE D. SAUNDERS, OF WILKINS- IBURG, PENNSYLVANIA, ASSIGNORS TO THE WESTINGHOUSE AIR BRAKE COMPANY, OF WILMEIRDING, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

PUMP-UNLOAIDING DEVICE.

Specification of Letters Patent.

Patented May 1, 1917.

Application filed July 12, 1915. Serial No. 39,291.

To all whom it may concern:

Be it known that we, PHILIP L. CRITTEN- DEN and LAWRENCE D. SAUNDERS, citizens of the United States, residents, respectively, of Edgewood and WVilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Pump-Unloading Devices, of which the following is a specification.

This invention relates to motor driven compressors, and more particularly to a de- Vice for relieving the motor of its load until a desired or normal speed of the motor is attained.

The principal object of the invention is to provide an improved device of the above character, in which the motor can run without load in starting for a definite number of revolutions.

In the accompanying drawings; Figure 1 is a side elevation, in part, of a motor driven compressor, with our improved unloading device, partly in section, applied thereto, and showing the parts in the cut-out position; Fig. 2 a similar view of the unloading device, with a portion of the ratchet bar broken away, and showing the parts in position when the compressor is started; Fig. 3 a partial end elevation of the motor compressor with the unloading device applied,

and- Fig. 1- a section on the line A-A- of Fig. 3. v a

The unloading device is preferably constructed to effect the unloading of the compressor motor by lifting the suction valves of the compressor during the starting period, so that during this time, there will be no compression of fluid by the compressor.

Accordingly, the one or more suction valves 1 of the compressor 2 are each adapted to be-lifted from its seat by a' rod 3, adapted to be guided in suitable bearings provided on the compressor casing and having an arm 4 carried at the lower end. A crank shaft-5 is mounted in bearings on the compressor casing in position to engage the arm 4; during the rotative movement thereof, so as to eflect the downward movement of the rod 3 to permit the suction valve 1 to seat, a spring 6 surrounding the rod 3, being adapted to force the rod upwardly for iunseating the valve 1 when the arm 4: is not engaged by the crank shaft.

At one end, the crank shaft 5 carries a ratchet wheel 7, the teeth of which are adapted to be engaged by the tooth 8 of a pawl bar 9. On the main shaft '10 of the compressor is secured an eccentric disk 11 adapted to engage the end of a reciprocating pm 12 pivotally connected tothe outer end of the pawl bar 9, said pin being pressed against the eccentric 11 by a spring .13.

The inner endof the pawl bar 9 is provided with a projection ll'adapted to engage in a corresponding recess 15 in the ratchet wheel 7 when the wheel isrotated to the registering position. A stout coil spring 16 has one end secured to, a casting 17 bolted to the compressor casing and the other end to a pin 18 mounted eccentrically on the ratchet wheel 7, so that the rotation of the ratchet wheel stretches the spring. A pawl 19 pivoted to the casting 17, engages the teeth of the ratchet wheel 7 for preventing the return movement thereof.

For throwing the pawl bar 9 into and out of engagement with the ratchet wheel 7, a fluid pressure operated piston 20 is provided, the piston being contained in a casing 21 having a pipe 22 leading to the piston chamber 23 at one side of the piston. A piston rod 21 is secured to the piston 20 and carries a yoke 25 at the upper end, within whichthe-pawl bar 9 works, said bar being maintained within the yoke by 'means of a pin 26.

When the compressor is out out of action, the pawl bar 9 is designed to be operated by the piston 20 to throw the tooth 8 out of engagement with the teeth of'the ratchet wheel 7 and when the compressor is cut' in, said tooth is thrown into engagement with the ratchet wheel. For this purpose, the pipe 22 is preferably connected to an electric pump governor, such as that shown in Patent No. 879,699, dated February 18, 1908, for example.

In this governor, the piston which operates the switch for controlling the pump motor circuit, is supplied with fluid under pressure to open the switch and fluid is vented from said piston to close the switch, so that by connecting the pipe 22 to the piston chamber of the governor, the piston 20 will also be subjected to fluid pressure when the pump motor is cut out, to throw the tooth 8 out of engagement with the ratchet wheel 7 and fluid 'will be vented from said piston when the pump motor is cut in to efiect the engagement of said tooth with the teeth of the ratchet wheel.

, In operation, when the pump governor is operated to close the pump motor circuit and start the motor, fluid is vented from piston 20, so that the spring 27 operates the pawl bar 9 to throw tooth 8 into engagement with the teeth of the ratchet wheel 7.

The parts of the unloading device are now in the positions shown in Fig. 2 of the drawings, with the crank portion of the shaft 5 in the position shown in dotted lines.

With the crank shaft 5 in the position shown in Fig. 2, the finger 4 is out of engagement therewith, so that spring 6 operates on the rod 3 to lift same and with it the suction valve 1. The suction valves of the compressor being thus opened, the compressor starts without load, as will be understood.

As the main compressor shaft 10 rotates, the eccentric disk 11 engages the pin 12 at each revolution and moves said pin so that the tooth 8 is operated through the pawl bar 9 to rotate the ratchet wheel 7 one tooth for each revolution of the compressor shaft. The pin 18 is carried around by the rotation of the ratchet wheel 7 and thereby stretches the spring 16, the ratchet wheel being prevented from moving backwardly by the engagement of the pawl 19 therewith.

When the compressor shaft has made a predetermined number of revolutions, the ratchet wheel will have been turned, so that the spring pin 18 will cross the axis of aline ment through the aXis of the ratchet wheel and then the force of the spring 16 will be exerted to turn the ratchet wheel with a quick movement, independently of the pawl bar, until the recess 15 has been brought to a position where the projection 11 on the pawl bar 9 engages same.

This movement causes the rotation of the crank shaft 5 so that same engages the finger 4 of the valve rod 3 and thereby depresses the finger and the rod 3 so as to permit the suction valves 1 to close. The closing of the suction valves then allows the compressor to operate thereafter in the usual manner to compress fluid.

The spring 16 has suflicient force so that when the projection 14: engages in the recess 15, the pawl bar 9 will be pulled over through the rotation of the ratchet wheel by the spring, until a shoulder 28 on the pin 12 engages the cap 29, as shown in Fig. 1 of the drawings. By this means, the pin 12 is drawn out, so that the rotation of the cam disk 11 will not eflect the movement thereof and the compressor will then operate with the unloading device cut out.

When the pump pressure has risen to the degree at which the pump motor is cut out and the compressor stopped, fluid is admitted to the piston 20 at the same time fluid is admitted to the governor switch piston to open the motor circuit and the piston 20 thereupon operates the pawl bar 9 to throw the projection ll out of engagement with the recess of the ratchet wheel 7 The spring 16 then returns to the normal position shown in Fig. 2, carrying with it the ratchet wheel 7, so that the parts are again in position for the tooth 8 to engage the ratchet wheel and rotate the same, when the compressor motor is started and the piston 20 operates the pawl bar 9 to throw the tooth 8 into engagement with the ratchet wheel.

It will now be evident that with the above described unloading device, the compressor and motor will operate without load until a definite predetermined number of revolutions has been made.

Having now described our invention, what we claim as new and desire to secure by Letters Patent, is:

1. The combination with a compressor shaft and a compressor suction valve, of means tending to maintain said valve inoperative and a crank for operating said means, and an operative connection between said crank and said compressor shaft.

2. The combination with a compressor shaft and a compressor suction valve, of means tending to maintain said valve inoperative, a crank mechanism for actuating said means to render the suction valve operative, a ratchet mechanism operated by the rotation of the compressor shaft for rotating the crank mechanism, and a spring adapted to be strained by the rotation of the ratchet mechanism through a part of its revolution for effecting the further rotation of said ratchet mechanism to thereby operate said crank mechanism and said means.

3. The combination with a compressor shaft and a compressor suction valve, of means tending to maintain said valve inoperative, a crank shaft adapted to engage said means at a certain point in the revolution thereof and thereby operate said means to render the suction valve operative, a ratchet wheel carried by said crank shaft, a pawl bar operated at each revolution of the compressor shaft for turning the ratchet wheel, a spring adapted to be strained by the turning of the ratchet wheel through a certain arc and adapted upon further movement of the ratchet wheel to exert its power to suddenly rotate the ratchet wheel through an additional arc and thereby cause the crank shaft to actuate said means for rendering the suction valve operative.

4. The combination with a compressor shaft, of a ratchet wheel, the rotation of which is adapted to control the loading and unloading of the compressor, a spring adapted to be strained by the rotation of the ratchet wheel through one portion of its revolution and adapted to eXert its power for rotating the ratchet wheel through another portion of its revolution, an eccentric carried by the compressor shaft, and a pawl bar operated by the eccentric for turning said ratchet wheel through the first mentioned portion of its revolution and adapted to be thrown out of operative engagement with the eccentric by the rotation of the ratchet wheel through the last mentioned portion of its revolution.

5. The combination with a compressor shaft, of a ratchet wheel, the rotation of which is adapted to control the loading and unloading of the compressor, a pawl bar operated by the rotation of the compressor I shaft for turning said ratchet wheel, and a piston operated by fluid under pressure when the compressor is cut out for throwing the pawl bar out of operative engagement with the ratchet wheel.

6. The combination with a compressor shaft, of a ratchet wheel, the rotation of which is adapted to control the loading and unloading of the compressor, a pawl bar for engaging the ratchet wheel and adapted to be operated by the rotation of the compressor shaft, a spring adapted to be first strained by the rotation of the ratchet wheel and then adapted to exert its stored power to rotate the ratchet wheel, a recess in said ratchet wheel, and a projection carried by said pawl ratchet bar for engaging the recess upon rotation of the wheel by the spring, to thereby render said pawl bar inoperative through rotation of the compressor shaft.

In testimony whereof we have hereunto set our hands.

PHILIP L. CRITTENDEN. LAWRENCE D. SAUNDERS.

Witnesses: c

A. M. CLEMENTs, BARBARA HERBERT.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

